This invention relates generally to special effects generators for television, and more particularly, to analog special effects generators capable of producing relatively complex patterns such as stars, hearts, keyhole, binocular and other patterns.
Special effects generators are well known, and can be divided into two general categories, namely, those utilizing analog circuitry to generate the special effects and those that utilize digital circuitry. Analog circuitry has heretofore been utilized in special effects generators that are capable of generating only relatively simple effects such as wipes wherein one image is wiped off of the screen by another, fades, wherein one image fades into another and inserts, wherein a square or rectangular portion of one video image is inserted into another video image. In order to avoid unduly complex circuitry, the inserts have been typically limited to square or rectangular inserts, and the wipes have been limited to horizontal or vertical wipes where the line separating the two images moves horizontally or vertically across the screen. More complicated rotational wipes such as "pinwheel" or "propeller" wipes are described in U.S. Pat. No. 3,812,286.
Because of the drift and periodic adjustment problems typically associated with analog circuitry, it has heretofore been advantageous to utilize digital circuitry when a special effects generator capable of producing complex effects was desired. Digital circuitry was used because analog circuitry required to produce complex special effects was rather complex, and the complex analog circuitry capable of producing such effects would require more maintenance and periodic adjustment than digital circuitry capable of providing the same function. A typical digital special effects generator is described in U.S. Pat. No. 3,821,468.
While the prior art analog special effects generators are useful in applications where only a limited number of special effects are desired, they are typically incapable of generating relatively complex patterns such as stars, hearts, keyholes, binocular patterns and other more intricate patterns such as triangles and V-shaped wipes. Digital special effects generators are capable of producing more complex patterns than typical analog special effects generators; however, digital special effects generators are considerably more complex than analog special effects generators, and therefore tend to be very costly.